AST (aspartate aminotransferase)
Also known as: AST, aspartate transaminase, SGOT
An enzyme found in liver cells but also in heart, skeletal muscle, kidney, brain and red cells. It rises with liver injury alongside ALT, and the AST:ALT ratio helps point towards or away from alcohol-related liver disease.
- Also known as
- AST, aspartate transaminase, SGOT
- Units
- U/L (units per litre)
- Measured by
- Liver function tests
What it is and what it does
AST is present both in the cytoplasm and in the mitochondria of cells, and it is far less specific to the liver than ALT. In hepatocellular injury both enzymes rise; in alcohol-related liver disease AST is typically higher than ALT (a ratio above 2), partly because alcohol depletes the vitamin B6 that ALT needs and damages mitochondria. Muscle injury, a heart attack, haemolysis and vigorous exercise all raise AST with little change in ALT, so an isolated AST elevation prompts a creatine kinase test. In advanced fibrosis the ratio flips because ALT production falls, which is why AST-based scores (such as APRI and FIB-4) are used to estimate scarring.
Why it may be higher
- All causes of hepatocellular injury: hepatitis, fatty liver, drugs, alcohol, ischaemia
- Alcohol-related liver disease (AST greater than ALT)
- Muscle disease or injury, rhabdomyolysis, strenuous exercise, seizures
- Heart attack, haemolysis, pancreatitis, coeliac disease
- Cirrhosis with advanced fibrosis (AST:ALT ratio rises)
Why it may be lower
- Low values are not clinically important; chronic kidney disease and B6 deficiency can lower them
A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.
What can affect the result
- Exercise in the preceding days, intramuscular injections, muscle bruising
- Haemolysed samples read falsely high
- Alcohol intake and medicines
Medicines that can change it
Each medicine page lists its effect on this marker under "Effects on tests and results", with the source.